/**
 * @file
 * API functions for name resolving
 *
 */

/*
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 *
 * This file is part of the lwIP TCP/IP stack.
 *
 * Author: Simon Goldschmidt
 *
 */

#include "lwip/netdb.h"

#if LWIP_DNS && LWIP_SOCKET

#include "lwip/err.h"
#include "lwip/mem.h"
#include "lwip/memp.h"
#include "lwip/ip_addr.h"
#include "lwip/api.h"
#include "lwip/dns.h"

#include <string.h>
#include <stdlib.h>

/** helper struct for gethostbyname_r to access the char* buffer */
struct gethostbyname_r_helper {
	ip_addr_t* addr_list[2];
	ip_addr_t addr;
	char* aliases;
};

/** h_errno is exported in netdb.h for access by applications. */
#if LWIP_DNS_API_DECLARE_H_ERRNO
	int h_errno;
#endif /* LWIP_DNS_API_DECLARE_H_ERRNO */

/** define "hostent" variables storage: 0 if we use a static (but unprotected)
 * set of variables for lwip_gethostbyname, 1 if we use a local storage */
#ifndef LWIP_DNS_API_HOSTENT_STORAGE
	#define LWIP_DNS_API_HOSTENT_STORAGE 0
#endif

/** define "hostent" variables storage */
#if LWIP_DNS_API_HOSTENT_STORAGE
	#define HOSTENT_STORAGE
#else
	#define HOSTENT_STORAGE static
#endif /* LWIP_DNS_API_STATIC_HOSTENT */

/**
 * Returns an entry containing addresses of address family AF_INET
 * for the host with name name.
 * Due to dns_gethostbyname limitations, only one address is returned.
 *
 * @param name the hostname to resolve
 * @return an entry containing addresses of address family AF_INET
 *         for the host with name name
 */
struct hostent*
lwip_gethostbyname(const char* name)
{
	err_t err;
	ip_addr_t addr;

	/* buffer variables for lwip_gethostbyname() */
	HOSTENT_STORAGE struct hostent s_hostent;
	HOSTENT_STORAGE char* s_aliases;
	HOSTENT_STORAGE ip_addr_t s_hostent_addr;
	HOSTENT_STORAGE ip_addr_t* s_phostent_addr[2];

	/* query host IP address */
	err = netconn_gethostbyname(name, &addr);

	if(err != ERR_OK) {
		LWIP_DEBUGF(DNS_DEBUG, ("lwip_gethostbyname(%s) failed, err=%d\n", name, err));
		h_errno = HOST_NOT_FOUND;
		return NULL;
	}

	/* fill hostent */
	s_hostent_addr = addr;
	s_phostent_addr[0] = &s_hostent_addr;
	s_phostent_addr[1] = NULL;
	s_hostent.h_name = (char*)name;
	s_hostent.h_aliases = &s_aliases;
	s_hostent.h_addrtype = AF_INET;
	s_hostent.h_length = sizeof(ip_addr_t);
	s_hostent.h_addr_list = (char**)&s_phostent_addr;

#if DNS_DEBUG
	/* dump hostent */
	LWIP_DEBUGF(DNS_DEBUG, ("hostent.h_name           == %s\n", s_hostent.h_name));
	LWIP_DEBUGF(DNS_DEBUG, ("hostent.h_aliases        == %p\n", s_hostent.h_aliases));

	if(s_hostent.h_aliases != NULL) {
		u8_t idx;

		for(idx = 0; s_hostent.h_aliases[idx]; idx++) {
			LWIP_DEBUGF(DNS_DEBUG, ("hostent.h_aliases[%i]->   == %p\n", idx, s_hostent.h_aliases[idx]));
			LWIP_DEBUGF(DNS_DEBUG, ("hostent.h_aliases[%i]->   == %s\n", idx, s_hostent.h_aliases[idx]));
		}
	}

	LWIP_DEBUGF(DNS_DEBUG, ("hostent.h_addrtype       == %d\n", s_hostent.h_addrtype));
	LWIP_DEBUGF(DNS_DEBUG, ("hostent.h_length         == %d\n", s_hostent.h_length));
	LWIP_DEBUGF(DNS_DEBUG, ("hostent.h_addr_list      == %p\n", s_hostent.h_addr_list));

	if(s_hostent.h_addr_list != NULL) {
		u8_t idx;

		for(idx = 0; s_hostent.h_addr_list[idx]; idx++) {
			LWIP_DEBUGF(DNS_DEBUG, ("hostent.h_addr_list[%i]   == %p\n", idx, s_hostent.h_addr_list[idx]));
			LWIP_DEBUGF(DNS_DEBUG, ("hostent.h_addr_list[%i]-> == %s\n", idx, ip_ntoa((ip_addr_t*)s_hostent.h_addr_list[idx])));
		}
	}

#endif /* DNS_DEBUG */

#if LWIP_DNS_API_HOSTENT_STORAGE
	/* this function should return the "per-thread" hostent after copy from s_hostent */
	return sys_thread_hostent(&s_hostent);
#else
	return &s_hostent;
#endif /* LWIP_DNS_API_HOSTENT_STORAGE */
}

/**
 * Thread-safe variant of lwip_gethostbyname: instead of using a static
 * buffer, this function takes buffer and errno pointers as arguments
 * and uses these for the result.
 *
 * @param name the hostname to resolve
 * @param ret pre-allocated struct where to store the result
 * @param buf pre-allocated buffer where to store additional data
 * @param buflen the size of buf
 * @param result pointer to a hostent pointer that is set to ret on success
 *               and set to zero on error
 * @param h_errnop pointer to an int where to store errors (instead of modifying
 *                 the global h_errno)
 * @return 0 on success, non-zero on error, additional error information
 *         is stored in *h_errnop instead of h_errno to be thread-safe
 */
int
lwip_gethostbyname_r(const char* name, struct hostent* ret, char* buf,
                     size_t buflen, struct hostent** result, int* h_errnop)
{
	err_t err;
	struct gethostbyname_r_helper* h;
	char* hostname;
	size_t namelen;
	int lh_errno;

	if(h_errnop == NULL) {
		/* ensure h_errnop is never NULL */
		h_errnop = &lh_errno;
	}

	if(result == NULL) {
		/* not all arguments given */
		*h_errnop = EINVAL;
		return -1;
	}

	/* first thing to do: set *result to nothing */
	*result = NULL;

	if((name == NULL) || (ret == NULL) || (buf == NULL)) {
		/* not all arguments given */
		*h_errnop = EINVAL;
		return -1;
	}

	namelen = strlen(name);

	if(buflen < (sizeof(struct gethostbyname_r_helper) + namelen + 1 + (MEM_ALIGNMENT - 1))) {
		/* buf can't hold the data needed + a copy of name */
		*h_errnop = ERANGE;
		return -1;
	}

	h = (struct gethostbyname_r_helper*)LWIP_MEM_ALIGN(buf);
	hostname = ((char*)h) + sizeof(struct gethostbyname_r_helper);

	/* query host IP address */
	err = netconn_gethostbyname(name, &h->addr);

	if(err != ERR_OK) {
		LWIP_DEBUGF(DNS_DEBUG, ("lwip_gethostbyname(%s) failed, err=%d\n", name, err));
		*h_errnop = HOST_NOT_FOUND;
		return -1;
	}

	/* copy the hostname into buf */
	MEMCPY(hostname, name, namelen);
	hostname[namelen] = 0;

	/* fill hostent */
	h->addr_list[0] = &h->addr;
	h->addr_list[1] = NULL;
	h->aliases = NULL;
	ret->h_name = hostname;
	ret->h_aliases = &h->aliases;
	ret->h_addrtype = AF_INET;
	ret->h_length = sizeof(ip_addr_t);
	ret->h_addr_list = (char**)&h->addr_list;

	/* set result != NULL */
	*result = ret;

	/* return success */
	return 0;
}

/**
 * Frees one or more addrinfo structures returned by getaddrinfo(), along with
 * any additional storage associated with those structures. If the ai_next field
 * of the structure is not null, the entire list of structures is freed.
 *
 * @param ai struct addrinfo to free
 */
void
lwip_freeaddrinfo(struct addrinfo* ai)
{
	struct addrinfo* next;

	while(ai != NULL) {
		next = ai->ai_next;
		memp_free(MEMP_NETDB, ai);
		ai = next;
	}
}

/**
 * Translates the name of a service location (for example, a host name) and/or
 * a service name and returns a set of socket addresses and associated
 * information to be used in creating a socket with which to address the
 * specified service.
 * Memory for the result is allocated internally and must be freed by calling
 * lwip_freeaddrinfo()!
 *
 * Due to a limitation in dns_gethostbyname, only the first address of a
 * host is returned.
 * Also, service names are not supported (only port numbers)!
 *
 * @param nodename descriptive name or address string of the host
 *                 (may be NULL -> local address)
 * @param servname port number as string of NULL
 * @param hints structure containing input values that set socktype and protocol
 * @param res pointer to a pointer where to store the result (set to NULL on failure)
 * @return 0 on success, non-zero on failure
 */
int
lwip_getaddrinfo(const char* nodename, const char* servname,
                 const struct addrinfo* hints, struct addrinfo** res)
{
	err_t err;
	ip_addr_t addr;
	struct addrinfo* ai;
	struct sockaddr_in* sa = NULL;
	int port_nr = 0;
	size_t total_size;
	size_t namelen = 0;

	if(res == NULL) {
		return EAI_FAIL;
	}

	*res = NULL;

	if((nodename == NULL) && (servname == NULL)) {
		return EAI_NONAME;
	}

	if(servname != NULL) {
		/* service name specified: convert to port number
		 * @todo?: currently, only ASCII integers (port numbers) are supported! */
		port_nr = atoi(servname);

		if((port_nr <= 0) || (port_nr > 0xffff)) {
			return EAI_SERVICE;
		}
	}

	if(nodename != NULL) {
		/* service location specified, try to resolve */
		err = netconn_gethostbyname(nodename, &addr);

		if(err != ERR_OK) {
			return EAI_FAIL;
		}
	} else {
		/* service location specified, use loopback address */
		ip_addr_set_loopback(&addr);
	}

	total_size = sizeof(struct addrinfo) + sizeof(struct sockaddr_in);

	if(nodename != NULL) {
		namelen = strlen(nodename);
		LWIP_ASSERT("namelen is too long", (namelen + 1) <= (mem_size_t) -1);
		total_size += namelen + 1;
	}

	/* If this fails, please report to lwip-devel! :-) */
	LWIP_ASSERT("total_size <= NETDB_ELEM_SIZE: please report this!",
	            total_size <= NETDB_ELEM_SIZE);
	ai = (struct addrinfo*)memp_malloc(MEMP_NETDB);

	if(ai == NULL) {
		goto memerr;
	}

	memset(ai, 0, total_size);
	sa = (struct sockaddr_in*)((u8_t*)ai + sizeof(struct addrinfo));
	/* set up sockaddr */
	inet_addr_from_ipaddr(&sa->sin_addr, &addr);
	sa->sin_family = AF_INET;
	sa->sin_len = sizeof(struct sockaddr_in);
	sa->sin_port = htons((u16_t)port_nr);

	/* set up addrinfo */
	ai->ai_family = AF_INET;

	if(hints != NULL) {
		/* copy socktype & protocol from hints if specified */
		ai->ai_socktype = hints->ai_socktype;
		ai->ai_protocol = hints->ai_protocol;
	}

	if(nodename != NULL) {
		/* copy nodename to canonname if specified */
		ai->ai_canonname = ((char*)ai + sizeof(struct addrinfo) + sizeof(struct sockaddr_in));
		MEMCPY(ai->ai_canonname, nodename, namelen);
		ai->ai_canonname[namelen] = 0;
	}

	ai->ai_addrlen = sizeof(struct sockaddr_in);
	ai->ai_addr = (struct sockaddr*)sa;

	*res = ai;

	return 0;
memerr:

	if(ai != NULL) {
		memp_free(MEMP_NETDB, ai);
	}

	return EAI_MEMORY;
}

#endif /* LWIP_DNS && LWIP_SOCKET */
